Storage virtualization switches (hereafter referred to as virtualization switch devices) are devices for integrally controlling physical volumes of multiple disk units and showing the physical volumes to the host computer as logical volumes. Such a virtualization switch device is commonly connected to a disk device including multiple disk units and to a server that makes a request to the virtualization switch devices, via lines such as fiber channels.
Among disk devices is one including a control module (hereafter referred to as a CM) that controls multiple disks under its command.
Connected to such a CM via disk adaptors (DA) or the like are multiple disk units. The virtualization switch device accesses the disk units via the CM.
Such storage systems include one that makes the virtualization switch device redundant by including multiple virtualization switch devices and enabling a controller, the server, to access each virtualization switch device. This configuration allows reducing the load imposed on each virtualization switch device in the storage system, as well as continuously operating the entire system even when any of the virtualization switch devices goes down.
Accordingly, in the related-art controller, it is difficult to distribute the load in accordance with the load situation of the actual CMs or disk units, although it is possible to distribute the load corresponding to the logical volumes. In particular, in a copy process, reading of data and writing of the data are performed on multiple disk units. Thus, depending on which of the virtualization switch devices the server instructs to perform the copy process, performance often significantly varies.
Japanese Laid-open Patent Publication (Translation of PCT Application) No. 2005-505035